Art. II.] Herrick, Gustatory Paths in Fishes. 105 



3. Chief tertiary gustatory neurones. 



G. TR.A.CTUS GUSTUS TERTIUS. 



1. Ad lobum inferiorem. 



2. Ad cerebellum. 



3. Ad mesencephalon. 



4. Ad substantiam reticularem. 



A detailed discussion of the mammalion homologies of the 

 tracts and nuclei enumerated in the preceding table is as yet 

 premature. Much further work on the intermediate types re- 

 mains to be done before such comparisons can have much value 

 except as suggestions for further research. 



In the human body the lingual branch of the glossopharyn- 

 geal nerve (from taste buds at the base of the tongue) undoubt- 

 edly corresponds to a portion of the pre-trematic branch of the 

 same nerve in fishes. The course of the peripheral gustatory 

 nerve from the taste buds at the tip of the tongue is still dis- 

 puted, though the evidence is rapidly accumulating that this 

 course is via the lingual nerve, chorda tympani and portio in- 

 termedia of Wrisberg into the fasciculus solitarius. The hom- 

 ologies of the chorda tympani have given comparative anatom- 

 ists a world of trouble. If the gustatory component of the 

 chorda in man supplies taste buds on the tip of the tongue, it 

 is obvious that in the fishes there can be no strictly homologous 

 nerve, for there is no fleshy tongue in fishes. From what 

 branch of the piscine facial nerve the mammalian chorda tym- 

 pani has been specialized is uncertain — possibly from none of 

 them. 



The identification of the fasciculus communis of amphibia 

 with the fasciculus solitarius of mammals was a very important 

 step in advance. In the teleosts the case is much more com- 

 plicated and difficult of correlation. But the descriptions of 

 Cajal ('96, p. 43) permit comparisons which are very close in 

 all fundamental respects. In the new-born mouse there is a 

 single sensory root for the vagus and glossopharyngeus and a 

 single terminal nucleus which is the grey substance associated 

 with the fasciculus solitarius. In addition to the dorsal nucleus 

 of KoLLiKER, which is a specialized portion of this substance, 

 there is another and more important specialization from it in the 



